Prior art photocoagulators generally have used such an ion laser as an argon laser but have been defective in that the photocoangulators are large in size and have employed a water cooling system.
In order to overcome such defects, there has been proposed an attempt to use a semiconductor laser which is small in size and based on an air cooling system. However, such an existing semiconductor laser can have an output as low as at most about 1.5 W. In addition, since the laser beam emitted from the optical fiber spreads more widely than an ion laser beam or the like, the semiconductor laser cannot produce a sufficient output power. For the purpose of increasing the quantity or power of laser beam to be directed to the input end of the optical fiber for laser beam to obtain a sufficient output power, there has been proposed such a method that two light sources of semiconductor are provided to combine laser beams emitted from the respective light sources with use of a polarizer or the like.
As the clinical application of the photocoagulator using the semiconductor laser is recently increased, transscleral cyclophotocoagulation by a semiconductor laser has been attempted for the purpose of reducing the intraocular pressure in glaucoma treatments.
However, even when the prior art photocoagulator using two laser light sources is employed, the photocoagulator has not been able to produce an output power as high as effective for the transscleral cyclophotocoagulation, because the resultant laser beam, i.e., the output power from the optical fiber of the photocoagulator is as low as at most about 2 W.
Theoretically, the output of the photocoagulator can be increased as the number of laser light sources built in the photocoagulator is increased. In actual applications, however, since the photocoagulator is complicated in laser beam combination manner and also poor in beam combination efficiency, such a photocoagulator that can be made compact and can produce an effective output power has not existed so far.